Journal of Materials Research


Thermodynamic Evaluation of the Interface Stability Between Selected Metal Oxides and Co

Ying Yanga1 c1, Peter F. Ladwiga2, Y. Austin Changa3, Feng Liua4, Bharat. B. Panta4 and Allan E. Schultza4

a1 Materials Science and Engineering Department, University of Wisconsin, Madison, Wisconsin 53706

a2 Materials Science Program, University of Wisconsin, Madison, Wisconsin, 53706

a3 Materials Science and Engineering Department and Materials Science Program, University of Wisconsin, Madison, Wisconsin 53706

a4 Recording Head Operations, Seagate Technology, Bloomington, Minnesota 55435


For an interface to be considered thermodynamically stable, the phases in contact must be in equilibrium with each other (connected by a stable tie-line) and have negligible mutual solubility on the phase diagram. The stability of Co based magnetic tunnel junctions (MTJs), with Co/MxO1-x/Co structures (M = Al, Gd, Hf, La, Mg, Si, Ti, Ta, Y and Zr), were evaluated with regard to these two conditions. Specifically, low temperature ternary isothermal phase diagrams were calculated and evaluated for the Co–M–O systems. All of these systems have at least one oxide in equilibrium with Co and thus have at least one thermodynamically stable tunnel barrier candidate for use in Co based MTJs. In light of the assumptions made in this analysis, along with the uncertainty in applying bulk enthalpy data to thin films, the current evaluation of interfacial stability serves as a first step in identifying suitable stable tunneling barrier materials in MTJs for detailed study.

(Received June 24 2003)

(Accepted January 07 2004)

Key Words:

  • Interface stability;
  • Thermodynamic properties;
  • Phase equilibria


c1 Address all correspondence to this author.